Dissolution behavior and solubility of anhydrous and trihydrate forms of ampicillin.

Anhydrous ampicillin and ampicillin trihydrate were compared for solubility and relative rates of dissolution in distilled water at temperatures ranging from 7.5 to 50°. Differences were noted in the physical-chemical properties of these two forms of ampicillin. The thermodynamic properties of these compounds have been experimentally evaluated. The properties noted for the two forms of the antibiotic are consistent with the observed differences in the biological utilization of the two forms after oral administration to laboratory animals and human subjects.